The changing epidemiology of leptospirosis in Israel.

We reviewed all serologically confirmed cases of leptospirosis from 1985 to 1999 in Israel, where the disease is endemic. There were 59 cases, with an average annual incidence of 0.05/100,000. The dominant serogroup, Leptospira icterohemorrhagica, occurred in 29% of patients; in an earlier study (1970-1979), it accounted for only 2%. Serogroups that occurred mainly in rural areas accounted previously for 79% but had declined to 32%. Leptospirosis, a zoonotic disease caused by a spirochete, is often related to occupation. Humans are infected through contact with animal reservoirs or a contaminated environment (soil, sewage, or water). Several animal species (rats, mice, or hedgehogs) are natural reservoirs of the disease, while humans are a dead-end host. Leptospira icterohemorrhagica is transmitted by rats and is found in sewage water. L. canicola, which is usually transmitted by dogs but rarely by cattle and swine, is common among field and irrigation workers. L. hardjo, which is transmitted mainly by cattle, is commonly found in dairy workers (1). The clinical spectrum of the disease depends on the serogroup and the host, ranging from a mild flulike illness to severe disease with multiple organ failure (Weil’s disease). Since 1950, Israel has been considered endemic for leptospirosis (1,2) with a peak incidence of 3.6/100,000 in the 1960s (3). From 1970 to 1979, 251 cases of leptospirosis were diagnosed, with a reported attack rate of 0.2/100,000, mainly in agricultural areas (1). Since 1979, no epidemiologic study has reported the prevalence of different serogroups and the epidemiologic pattern of the disease. We have reviewed all known cases of leptospirosis in Israel from 1985 through 1999.